Examples of widely known cutting tools include throw-away inserts used for turning and milling as well as end mills generally used for side milling, beveling, and fluting various types of metals, and drills used for boring. These end mills and drills are formed with a section that includes a cutting section, known as the body, and a section known as the shank that is mounted in a drive device. Examples of bodies include: solid bodies, where the body is formed integrally from a cutting section and a support that includes a flute for supporting the cutting section and allowing chips to be ejected; brazed bodies, where the cutting section is brazed to the support; and throw-away bodies, where the cutting section can be attached to and removed from the support. Conventionally, solid bodies are formed from high-speed tool steel or cemented carbide. Brazed bodies are formed by brazing a cutting section formed from a hard material such as cemented carbide to a support formed from high-speed tool steel.
In recent years, various cutting tool materials have been developed to meet the demand for higher efficiency and precision in cutting. In the process of developing these materials, ceramic coating technology, in which a coating layer formed from ceramics is applied to the surface of a tool substrate, has become a crucial technology in cutting tools. For example, the use of titanium-based ceramics, e.g., titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (Ti(C,N)), and oxide-based ceramics, e.g., alumina (Al2O3) and zirconia (ZrO2) to form coating layers for cutting tools used in high-speed, high-efficiency operations involving high speeds and high feeds is widely known. Japanese Laid-Open Patent Publication Number Hei 11-124672 describes a throw-away insert equipped with a coating layer with a defined X-ray diffraction index of orientation. This insert is used in high-speed, high-efficiency operations involving high speeds and high feeds. In addition to throw-away inserts, this type of ceramic coating technology is also becoming widely used in solid and brazed tools that are often used in end mills and drills.
The inclusion of a ceramic coating on a cutting tool improves surface hardness and heat resistance and allows the tool to handle high-speed, high-efficiency operations involving high speeds and high feeds. In addition to this type of high-speed, high-efficiency operation, in recent years attention has been given to methods that protect the environment such as mist cutting, where the use of cutting oil is drastically reduced, or dry cutting, where cutting oil is not used. To handle these types of operations, throw-away inserts equipped with a coating layer with superior welding resistance or a coating layer with a chip sliding feature (see Japanese Laid-Open Patent Publication Number Hei 10-158861 and Japanese Laid-Open Patent Publication Number 2003-225808), and a drill coated with a CrN film having lubricity (Japanese Laid-Open Patent Publication Number 2003-275911) have been proposed. In addition, cutting tools equipped with an aluminum nitride coating layer for improved heat dissipation and the like have been proposed (see Japanese Examined Patent Publication Number Sho 59-27382; Japanese Patent Publication Number 2861113; Japanese Laid-Open Patent Publication Number 2002-273607; Japanese Laid-Open Patent Publication Number 2002-263933; Japanese Laid-Open Patent Publication Number 2002-263941; Japanese Laid-Open Patent Publication Number 2003-19604; Japanese Laid-Open Patent Publication Number 2003-25112; and Japanese Examined Patent Publication Number Sho 59-27302.
However, all of the conventional cutting tools described above have insufficient lubricity, especially for mist cutting and dry cutting, in which no cutting oil is used. This leads to reduced tool life. Thus, there is a need to improve lubricity so that tool life can be extended. With end mills and drills in particular, high lubricity is important for increasing the ability of chips to be ejected out through the flute formed on the body. High lubricity is also preferable for cutting materials that tend to weld and for deep hole boring, where the ability of chips to be ejected out is important.